Modern aircraft turbine engines require small, light-weight components capable of withstanding temperature extremes. Engine efficiency, performance, and maintenance costs are significantly influenced by the thrust or axial load the engine places on the main shaft rolling element bearings. Historically, there have been several efforts to measure thrust load. These methods usually require complicated geometries or intricate fiber optic measurement methods. The measurement of thrust loads were previously unavailable, and therefore engine designs have relied upon complicated and often inaccurate mathematical models to determine thrust loads. Additionally, bearing life models used to ensure safety and robustness of main shaft bearings are based on rig testing rather than real world measurements. These limitations likely result in engines that are overdesigned and make it unnecessarily costly to build and/or operate. The ability to measure the real thrust load on a main shaft bearing enables significant improvements in the scientific knowledge, design, performance, and economy of turbine engines.
A simple and reliable method for measuring bearing thrust load in a turbine aircraft engine has remained elusive, largely due to the unique challenges of such an application. Some thrust load measurement devices rely on hydraulic thrust indication or require the use of fluid bearings, neither of which are suitable for a turbine aircraft engine. Other devices require placement directly on the centerline of the shaft which is not possible for a turbine engine. Many of the known devices are either large or heavy, both detrimental factors in the design of a modem, compact, lightweight aircraft engine. Innovative devices have been presented in recent years that would be suitable for such an application, however, these devices have been found to have significant disadvantages as well, i.e., such devices incorporate a deformable ring or wave washer for thrust measurements. It has been found that, depending on the instrumentation used, this type of device is detrimentally sensitive to instrumentation placement or requires twice as much instrumentation per measurement. Fiber optic sensors have also been proposed, however mechanical noise and contaminated or non-homogeneous environments present significant challenges to this type of technology.